Resist composition and patterning process

ABSTRACT

A copolymer of an alkali-soluble (α-trifluoromethyl)-acrylate and a norbornene derivative is useful as an additive to a resist composition. When processed by immersion lithography, the resist composition exhibits excellent water repellency and water slip and forms a pattern with few development defects.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2008-124476 filed in Japan on May 12, 2008,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention generally relates to a photolithography process for themicrofabrication of semiconductor devices, and particularly to animmersion photolithography process involving directing ArF excimer laserradiation having a wavelength of 193 nm from a projection lens toward aresist-coated substrate, with a liquid (e.g., water) intervening betweenthe lens and the substrate. More particularly, it relates to a resistcomposition for use in the lithography process and a process for forminga pattern using the same.

BACKGROUND ART

In the recent drive for higher integration and operating speeds in LSIdevices, the pattern rule is made drastically finer. The backgroundsupporting such a rapid advance is a reduced wavelength of the lightsource for exposure. The change-over from i-line (365 nm) of a mercurylamp to shorter wavelength KrF laser (248 nm) enabled mass-scaleproduction of dynamic random access memories (DRAM) with an integrationdegree of 64 MB (processing feature size≦0.25 μm). To establish themicropatterning technology necessary for the fabrication of DRAM with anintegration degree of 256 MB and 1 GB or more, the lithography using ArFexcimer laser (193 nm) is under active investigation. The ArF excimerlaser lithography, combined with a high NA lens (NA≧0.9), is consideredto comply with 65-nm node devices. For the fabrication of next 45-nmnode devices, the F₂ laser lithography of 157 nm wavelength became acandidate. However, because of many problems including a cost and ashortage of resist performance, the employment of F₂ lithography waspostponed. ArF immersion lithography was proposed as a substitute forthe F₂ lithography. Efforts have been made for the early introduction ofArF immersion lithography (see Proc. SPIE, Vol. 4690, xxix, 2002).

In the ArF immersion lithography, the space between the projection lensand the wafer is filled with water and ArF excimer laser is irradiatedthrough the water. Since water has a refractive index of 1.44 at 193 nm,pattern formation is possible even using a lens with NA of 1.0 orgreater. Theoretically, it is possible to increase the NA to 1.44. Theresolution is improved by an increment of NA. A combination of a lenshaving NA of at least 1.2 with ultra-high resolution technology suggestsa way to the 45-nm node (see Proc. SPIE, Vol. 5040, p 724, 2003).

Several problems arise when a resist film is exposed in the presence ofwater. For example, the acid once generated from a photoacid generatorand a basic compound added to the resist material can be partiallyleached in water. As a result, pattern profile changes and patterncollapse can occur. It is also pointed out that water droplets remainingon the resist film, though in a minute volume, can penetrate into theresist film to generate defects.

These drawbacks of the ArF immersion lithography may be overcome byproviding a protective coating between the resist film and water toprevent resist components from being leached out and water frompenetrating into the resist film (see 2nd Immersion Workshop: Resist andCover Material Investigation for Immersion Lithography, 2003).

With respect to the protective coating on the photoresist film, atypical antireflective coating on resist (ARCOR) process is disclosed inJP-A 62-62520, JP-A 62-62521, and JP-A 60-38821. The ARCs are made offluorinated compounds having a low refractive index, such asperfluoroalkyl polyethers and perfluoroalkyl amines. Since thesefluorinated compounds are less compatible with organic substances,fluorocarbon solvents are used in coating and stripping of protectivecoatings, raising environmental and cost issues.

Other resist protective coating materials under investigation includewater-soluble or alkali-soluble materials. See, for example, JP-A6-273926, Japanese Patent No. 2,803,549, and J. Photopolymer Sci. andTechnol., Vol. 18, No. 5, p 615, 2005. Since the alkali-soluble resistprotective coating material is strippable with an alkaline developer, iteliminates a need for an extra stripping unit and offers a great costsaving. From this standpoint, great efforts have been devoted to developwater-insoluble resist protective coating materials, for example, resinshaving alkali-soluble groups such as fluorinated alcohol, carboxyl orsulfo groups on side chains. See WO 2005/42453, WO 2005/69676, JP-A2005-264131, JP-A 2006-133716, and JP-A 2006-91798.

As means for preventing resist components from being leached out andwater from penetrating into the resist film without a need for aprotective coating material, it is proposed in JP-A 2006-48029, JP-A2006-309245, and JP-A 2007-187887 to add an alkali-soluble, hydrophobiccompound as a surfactant to the resist material. This method achievesequivalent effects to the use of resist protective coating materialbecause the hydrophobic compound is segregated at the resist surfaceduring resist film formation. Additionally, this method is economicallyadvantageous over the use of a resist protective film because steps offorming and stripping the protective film are unnecessary.

The ArF immersion lithography systems commercially available at thepresent are designed such that water is partly held between theprojection lens and the wafer rather than immersing the resist-coatedsubstrate fully in water, and exposure is carried out by scanning thewafer-holding stage at a speed of 300 to 550 nm/sec. In the event ofsuch high-speed scanning, unless the performance of the resist orprotective film is sufficient, water cannot be held between theprojection lens and the wafer, and water droplets are left on thesurface of the resist film or protective film after scanning. It isbelieved that residual droplets cause defective pattern formation.

To eliminate the droplets remaining on the surface of the photoresist orprotective film after scanning, it is necessary to improve the flow ormobility of water (hereinafter, water slip) on the relevant coatingfilm. It is reported that the number of defects associated with theimmersion lithography can be reduced by increasing the receding contactangle of the photoresist or protective film with water. See 2ndInternational Symposium on Immersion Lithography, Sep. 12-15, 2005,Defectivity data taken with a full-field immersion exposure tool, Nakanoet al.

One exemplary material known to have excellent water slip and waterrepellency on film surface is a copolymer of α-trifluoromethylacrylateand norbornene derivative (Proc. SPIE, Vol. 4690, p 18, 2002). Whilethis polymer was developed as the base resin for F₂ (157 nm) lithographyresist materials, it is characterized by a regular arrangement ofmolecules of α-trifluoromethylacrylate (effective for water repellencyimprovement) and norbornene derivative in a ratio of 2:1.

When a water molecule interacts with methyl and trifluoromethyl groups,it orients via its oxygen and hydrogen atoms, respectively, and theorientation distance between water and methyl is longer, as discussed inXXIV FATIPEC Congress Book, Vol. B, p 15 (1997) and Progress in OrganicCoatings, 31, p 97-104 (1997). A resin having not only water repellentfluorinated units introduced, but also both fluoroalkyl and alkyl groupsincorporated is improved in water slip because of a longer orientationdistance of water. In fact, a polymer having a regular arrangement ofwater repellent monomeric units like the above-referred copolymer ofα-trifluoromethylacrylate and norbornene derivative is used as the basepolymer in a protective coating for immersion lithography, water slip isdrastically improved (see US 20070122736 or JP-A 2007-140446).

A material having good water slip performance is also required from thestandpoint of productivity. The immersion lithography needs higherthroughputs than ever. For improved productivity, the exposure time mustbe reduced, which in turn requires high-speed scanning operation of thestage. In order to move the stage at a high speed while holding waterbeneath the lens, it is desired to have a resist material or resistprotective film having higher water slip performance.

The highly water repellent/water slippery materials discussed above areexpected to be applied not only to the ArF immersion lithography, butalso to the resist material for mask blanks. Resist materials for maskblanks suffer from problems including a change of sensitivity duringlong-term exposure in vacuum and long-term stability after coating. Withrespect to the control of sensitivity changes in vacuum, an improvementis made by a combination of acid labile groups of acetal and tertiaryester types (U.S. Pat. No. 6,869,744). It is believed that after coatingof a resist material, an amine component is adsorbed to the resist filmsurface whereby the resist varies its sensitivity or profile. A methodof modifying the surface of a resist film for preventing adsorption ofan amine component to the resist film has been devised.

Hydrophobic surfactants for use in resist protective coatings and resistmaterials are allegedly effective in overcoming a pattern profilechange, referred to as “dark-bright difference,” which is consideredproblematic in many types of lithography including immersionlithography, dry lithography and EB lithography. The dark-brightdifference is a phenomenon that the profile of a line-and-space patterndiffers between a bright pattern where a peripheral portion around thepattern is exposed and a dark pattern where a peripheral portion aroundthe pattern is not exposed. When a peripheral portion around the patternis exposed, the acid generated in the peripheral portion can evaporateduring PEB to cover the pattern area, whereby the line pattern undergoesa film slimming. When a peripheral portion around the pattern is notexposed, no acid is supplied from the peripheral portion and inversely,amine evaporates whereby the line pattern takes a bulged top profile.The “dark-bright difference” occurs by this mechanism. The dark-brightdifference can be reduced by providing a protective coating on theresist film.

Citation List Patent Document 1: JP-A S62-62520 Patent Document 2: JP-AS62-62521 Patent Document 3: JP-A S60-38821 Patent Document 4: JP-AH06-273926 Patent Document 5: JP 2803549 Patent Document 6: WO2005/42453 Patent Document 7: WO 2005/69676 Patent Document 8: JP-A2005-264131 Patent Document 9: JP-A 2006-133716 Patent Document 10: U.S.Pat. No. 7,455,952 (JP-A 2006-91798) Patent Document 11: JP-A2006-048029 Patent Document 12: JP-A 2006-309245 Patent Document 13:JP-A 2007-187887 Patent Document 14: US 20070122736 (JP-A 2007-140446)Patent Document 15: U.S. Pat. No. 6,869,744 Non-Patent Document 1: Proc.SPIE, Vol. 4690, xxix, 2002 Non-Patent Document 2: Proc. SPIE, Vol.5040, p724, 2003 Non-Patent Document 3: 2nd Immersion Workshop: Resistand Cover Material Investigation for Immersion Lithography (2003)Non-Patent Document 4: J. Photopolymer Sci. and Technol., Vol. 18, No.5, p615, 2005 Non-Patent Document 5: 2nd International Symposium onImmersion Lithography, 12-15 Sept., 2005, Defectivity data taken with afull-field immersion exposure tool, Nakano et al. Non-Patent Document 6:Proc. SPIE, Vol. 4690, p18 (2002) Non-Patent Document 7: XXIV FATIPECCongress Book, Vol. B, p15 (1997) Non-Patent Document 8: Progress inOrganic Coatings, 31, p97-104 (1997)

SUMMARY OF INVENTION

An object of the invention is to provide a resist composition which hasimproved water repellency and water slip and suffer from few developmentdefects; an additive polymer essential to achieve such performance; anda pattern forming process using the composition.

The inventors have discovered that a copolymer of an alkali-soluble(α-trifluoromethyl)acrylate and a norbornene derivative, designatedpolymer P1, P1′, P1″ or P2 (collectively referred to as polymer PA) isuseful as an additive to a photoresist composition for immersionlithography.

Accordingly, the present invention provides a resist composition and apattern forming process, as defined below.

In a first aspect, the invention provides a resist compositioncomprising (A) a polymer P1 comprising repeat units of the followinggeneral formulae (1a) and (2a), (B) a polymer having a structurecontaining one or both of a lactone ring and a hydroxyl group, and/or astructure derived from maleic anhydride, which polymer becomes solublein an alkaline developer under the action of an acid, (C) a compoundcapable of generating an acid upon exposure to high-energy radiation,and (D) an organic solvent.

Herein R^(1a) and R^(1b) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl, R^(1a) and R^(1b) may bond together to form a non-aromaticring with the carbon atom to which they are attached, R² is hydrogen,methyl or trifluoromethyl, R³ is hydrogen or an acid labile group, a1and b1 are numbers satisfying 0<a1<1, 0<b1<1, and 0<a1+b1≦1.

In a second aspect, the invention provides a resist compositioncomprising (A) a polymer P1′ comprising repeat units of the followinggeneral formulae (1a), (1b) and (2a), (B) a polymer having a structurecontaining one or both of a lactone ring and a hydroxyl group, and/or astructure derived from maleic anhydride, which polymer becomes solublein an alkaline developer under the action of an acid, (C) a compoundcapable of generating an acid upon exposure to high-energy radiation,and (D) an organic solvent.

Herein R^(1a), R^(1b), R² and R³ are as defined above, R^(4a) to R^(4c)are hydrogen or straight, branched or cyclic C₁-C₁₀ alkyl, and a1, a2and b1 are numbers satisfying 0<a1<1, 0<a2<1, 0<b1<1, and 0<a1+a2+b1≦1.

In a third aspect, the invention provides a resist compositioncomprising (A) a polymer P1″ comprising repeat units of the followinggeneral formulae (1a), (1b), (2a) and (2b), (B) a polymer having astructure containing one or both of a lactone ring and a hydroxyl group,and/or a structure derived from maleic anhydride, which polymer becomessoluble in an alkaline developer under the action of an acid, (C) acompound capable of generating an acid upon exposure to high-energyradiation, and (D) an organic solvent.

Herein R^(1a), R^(1b), R², R³, and R^(4a) to R^(4c) are as definedabove, R⁵ is straight, branched or cyclic C₁-C₁₀ alkyl, and a1, a2, b1and b2 are numbers satisfying 0<a1<1, 0≦a2<1, 0≦b1<1, 0<b2<1, and0<a1+a2+b1+b2≦1.

In a fourth aspect, the invention provides a resist compositioncomprising (A) a polymer P2 corresponding to a polymer P1-H comprisingrepeat units of the following general formulae (1a) and (2a′) whereinsome or all of hydroxyl groups in formulae (1a) and (2a′) are protectedwith protective groups, (B) a polymer having a structure containing oneor both of a lactone ring and a hydroxyl group, and/or a structurederived from maleic anhydride, which polymer becomes soluble in analkaline developer under the action of an acid, (C) a compound capableof generating an acid upon exposure to high-energy radiation, and (D) anorganic solvent.

Herein R^(1a), R^(1b), R², a1 and b1 are as defined above.

In any of the foregoing aspects, the resist composition may furthercomprise (E) a basic compound and/or (F) a dissolution inhibitor.

In a fifth aspect, the invention provides

a pattern forming process comprising the steps of (1) applying theresist composition defined above onto a substrate to form a resistcoating, (2) heat treating the resist coating and exposing it tohigh-energy radiation through a photomask, and (3) developing theexposed coating with a developer;

a pattern forming process comprising the steps of (1) applying theresist composition defined above onto a substrate to form a resistcoating, (2) heat treating the resist coating and exposing it tohigh-energy radiation from a projection lens through a photomask whileholding a liquid between the substrate and the projection lens, and (3)developing the exposed coating with a developer; and

a pattern forming process comprising the steps of (1) applying theresist composition defined above onto a substrate to form a resistcoating, (2) forming a protective coating onto the resist coating, (3)heat treating and exposing the coated substrate to high-energy radiationfrom a projection lens through a photomask while holding a liquidbetween the substrate and the projection lens, and (4) developing with adeveloper.

Typically, the liquid is water; and the high-energy radiation has awavelength in the range of 180 to 250 nm.

Also provided is a pattern forming process comprising the steps of (1)applying the resist composition defined above onto a mask blank to forma resist coating, (2) heat treating and exposing the resist coating invacuum to electron beam, and (3) developing with a developer.

ADVANTAGEOUS EFFECTS OF INVENTION

When applied to the immersion lithography, the resist composition of theinvention forms a resist film having a large receding contact angleenough to inhibit leaching-out of resist components and penetration ofwater into the resist film. It also ensures that the resist film isdeveloped into a satisfactorily profiled pattern with minimaldevelopment defects.

DESCRIPTION OF EMBODIMENTS

The singular forms “a”, “an” and “the” include plural referents unlessthe context clearly dictates otherwise.

The notation (Cn-Cm) means a group containing from n to m carbon atomsper group.

A. Polymer

The polymers P1, P1′ and P1″ used in the resist composition of theinvention are characterized by comprising repeat units having thegeneral formulae (1a), (1b), (2a), and (2b).

Herein R^(1a) and R^(1b) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl, or R^(1a) and R^(1b) may bond together to form anon-aromatic ring with the carbon atom to which they are attached. R² ishydrogen, methyl or trifluoromethyl. R³ is hydrogen or an acid labilegroup. R^(4a) to R^(4c) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl. R⁵ is straight, branched or cyclic C₁-C₁₀ alkyl. Thesubscripts a1, a2, b1 and b2 are numbers satisfying 0<a1<1, 0<a2<1,0<b1<1, 0<b2<1, 0<a1+a2<1, 0<b1+b2<1, and 0<a1+a2+b1+b2≦1.

The meaning of a1+a2+b1+b2=1 is that in a polymer comprising repeatunits (1a), (1b), (2a) and (2b), the total of repeat units (1a), (1b),(2a) and (2b) is 100 mol % based on the total amount of entire repeatunits. The sum of fractions of repeat units (1a) and (1b) is preferably20 to 80 mol %, and more preferably 30 to 70 mol %. The meaning ofa1+a2+b1+b2<1 is that the total of repeat units (1a), (1b), (2a) and(2b) is less than 100 mol % based on the total amount of entire repeatunits, indicating the inclusion of other repeat units.

In formulae (1b), (2a) and (2b), exemplary straight, branched or cyclicC₁-C₁₀ alkyl groups represented by R^(1a), R^(1b), R^(4a) to R^(4c), andR⁵ include, but are not limited to, methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-heptyl,n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,cyclohexylbutyl, and adamantyl. R^(1a) and R^(1b) may bond together toform a non-aromatic ring with the carbon atom to which they areattached, wherein each of R^(1a) and R^(1b) is alkylene, examples ofwhich include the foregoing alkyl groups with one hydrogen atomeliminated, and exemplary rings include cyclopentyl and cyclohexyl.

The acid labile group represented by R³ in formula (2a) may be selectedfrom a variety of such groups. Examples of the acid labile group aregroups of the following general formulae (L1) to (L4), tertiary alkylgroups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms,trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms,and oxoalkyl groups of 4 to 20 carbon atoms.

Herein, the broken line denotes a valence bond. In formula (L1), R^(L01)and R^(L02) are hydrogen or straight, branched or cyclic alkyl groups of1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Exemplary alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, n-octyl, andadamantyl. R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms, which may contain a heteroatomsuch as oxygen, examples of which include unsubstituted straight,branched or cyclic alkyl groups and substituted forms of such alkylgroups in which some hydrogen atoms are replaced by hydroxyl, alkoxy,oxo, amino, alkylamino or the like. Illustrative examples of thestraight, branched or cyclic alkyl groups are as exemplified above forR^(L01) and R^(L02), and examples of the substituted alkyl groups are asshown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may bond together to form a ring with carbon and oxygen atoms towhich they are attached. Each of ring-forming R^(L01), R^(L02) andR^(L03) is a straight or branched alkylene group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, and the like. Exemplarytrialkylsilyl groups are trimethylsilyl, triethylsilyl, anddimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl,4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxolan-5-yl. Letter y is aninteger of 0 to 6.

In formula (L3), R^(L05) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of the optionally substituted alkyl groupsinclude straight, branched or cyclic alkyl groups such as methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, cyclopentyl, cyclohexyl, and bicyclo[2.2.1]heptyl, andsubstituted forms of such groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups or inwhich some methylene groups are replaced by oxygen or sulfur atoms.Examples of optionally substituted aryl groups include phenyl,methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. Letter m isequal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or3.

In formula (L4), R^(L06) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of these groups are the same as exemplifiedfor R^(L05). R^(L07) to R^(L16) independently represent hydrogen ormonovalent hydrocarbon groups of 1 to 15 carbon atoms. Exemplaryhydrocarbon groups are straight, branched or cyclic alkyl groups such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl,cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl,cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl, and substitutedforms of these groups in which some hydrogen atoms are replaced byhydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino,cyano, mercapto, alkylthio, sulfo or other groups. Alternatively, two ofR^(L07) to R^(L16) may bond together to form a ring with the carbonatom(s) to which they are attached (for example, a pair of R^(L07) andR^(L08), R^(L07) and R^(L09), R^(L08) and R^(L10), R^(L09) and R^(L10),R^(L11) and R^(L12), R^(L13) and R^(L14), or a similar pair form aring). Each of R^(L07) to R^(L16) represents a divalent C₁-C₁₅hydrocarbon group when they form a ring, examples of which are thoseexemplified above for the monovalent hydrocarbon groups, with onehydrogen atom being eliminated. Two of R^(L07) to R^(L16) which areattached to vicinal carbon atoms may bond together directly to form adouble bond (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair).

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxy-n-butyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl.

Of the acid labile groups of formula (L4), those groups of the followingformulae (L4-1) to (L4-4) are preferred.

In formulas (L4-1) to (L4-4), the broken line denotes a bonding site anddirection. R^(L41) is each independently a monovalent hydrocarbon group,typically a straight, branched or cyclic C₁-C₁₀ alkyl group, such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Note that R^(L41) is as defined above.

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Note that R^(L41) is as defined above.

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of bicyclo[2.2.1]heptane structure as a substituent group, theremay be contained monomers substituted with an endo-alkyl group asrepresented by the following formulas (L4-1-endo) to (L4-4-endo). Forgood reactivity, an exo proportion of at least 50 mol % is preferred,with an exo proportion of at least 80 mol % being more preferred.

Note that R^(L41) is as defined above.

Illustrative examples of the acid labile group of formula (L4) are givenbelow

Examples of the tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups inwhich each alkyl moiety has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkylgroups, represented by R³, are as exemplified for R^(L04) and the like.

In the resist composition of the fourth aspect, the base polymer may bea polymer P2 corresponding to a polymer P1-H comprising repeat units ofthe general formulae (1a) and (2a′) as essential units wherein some orall of hydroxyl groups in either one or both of formula (1a) and formula(2a′) are protected with protective groups. It is acceptable that someor all hydroxyl groups in formulae (1a) and (2a′) be protected withprotective groups.

Herein R^(1a) and R^(1b) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl, or R^(1a) and R^(1b) may bond together to form anon-aromatic ring with the carbon atom to which they are attached. R² ishydrogen, methyl or trifluoromethyl. The subscripts a1 and b1 arenumbers satisfying 0<a1<1, 0<b1<1, and 0<a1+b1≦1.

As in the foregoing embodiment, the meaning of a1+b1=1 is that the totalof repeat units (1a) and (2a′) is 100 mol % based on the total amount ofentire repeat units. A proportion of repeat units (1a) is preferably 20to 80 mol %, and more preferably 30 to 70 mol %. The meaning of a1+b1<1is that the total of repeat units (1a) and (2a′) is less than 100 mol %based on the total amount of entire repeat units, indicating theinclusion of other repeat units.

In formula (2a′), exemplary straight, branched or cyclic C₁-C₁₀ alkylgroups represented by R^(1a) and R^(1b) include, but are not limited to,methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl,cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl,cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl,and adamantyl. R^(1a) and R^(1b) may bond together to form a ring asdescribed above, wherein each of R^(1a) and R^(1b) is alkylene, examplesof which include the foregoing alkyl groups with one hydrogen atomeliminated, and suitable rings are as exemplified above.

While the method of protecting hydroxyl groups on the polymer P1-Hcomprising repeat units of formulae (1a) and (2a′) will be describedlater, the protective groups used herein include acid labile groups asillustrated for R³ and straight, branched or cyclic C₁-C₁₀ alkyl groups.Exemplary straight, branched or cyclic C₁-C₁₀ alkyl groups include, butare not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-heptyl, n-octyl,n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,cyclohexylbutyl, and adamantyl.

In the polymer P2, a degree of protection of hydroxyl groups on polymerP1-H may vary from 0 mol % to 100 mol % of the entire hydroxyl groups.As a degree of protection is increased, water slip performance such assliding angle and receding contact angle can be enhanced. However, anexcessive increase in degree of protection results in a resin having areduced alkali dissolution rate. In practice, a polymer having a degreeof protection of hydroxyl groups in the range of 0 to 60 mol %, andpreferably 10 to 40 mol % is used for a balance of water slipperformance and alkali dissolution rate.

Illustrative, non-limiting examples of the repeat units of formula (1b)are given below.

Illustrative, non-limiting examples of the repeat units of formula (2a)are given below.

Herein R² and R³ are as defined above.

Illustrative, non-limiting examples of the repeat units of formula (2b)are given below.

Herein R² is as defined above.

In polymer PA used in the resist composition of the invention, therepeat unit of formula (1a) contributes to water repellency and alkalisolubility since it contains a hexafluoroalcohol group. The repeat unitsof formulae (1b), (2a) and (2b) exert excellent performance in waterrepellency and water slip despite poor alkali solubility. Because of acombination of these units, polymer PA exhibits excellent performance inwater repellency and water slip.

It is believed that the regular arrangement of α-trifluoromethylacrylatestructures and norbornene structures also contributes to the excellentwater slip of polymer PA.

As discussed in the literature listed above, a water molecule orientsvia its oxygen atom upon interaction with a methyl group, whereas itorients via its hydrogen atom upon interaction with a trifluoromethylgroup. It is reported in XXIV FATIPEC Congress Book, Vol. B, p 15 (1997)that the distances between H (methyl) and O (water molecule) and betweenF (trifluoromethyl) and H (water molecule) in these orientations are0.252 nm and 0.187 nm, respectively. For better water slip performance,a longer orientation distance of a water molecule is advantageous. Theabove fact implies that mere introduction of fluorine into a resin failsto increase the orientation distance of a water molecule and does notlead to a dramatic improvement in water slip performance.

In contrast, in a system where methyl and trifluoromethyl groups areregularly arranged, for example, if one hydrogen atom of a watermolecule orients to a trifluoromethyl group, the other hydrogen atom ofwater molecule is present in proximity to an adjacent methyl group, sothat a repulsion force develops between H (methyl) and H (watermolecule). As a result, the distance of orientation to water increasesto provide an improvement in water slip performance. For the samereason, polymers having a regular arrangement ofα-trifluoromethylacrylate structures and norbornene structures likepolymer PA exhibit better water slip performance than polymers whereintrifluoromethyl groups are randomly distributed within the polymerstructure (e.g., methacrylate polymers).

The scanning operation in the immersion lithography requires a highreceding contact angle in order to prevent liquid droplets from beingleft backward of scanning and a low advancing contact angle in order torestrain micro-bubbles from being entrained forward of scanning. Thisnecessitates a material having a little difference between advancing andreceding contact angles. Polymer PA is believed promising as ahydrophobic additive for a resist material in the immersion lithographysince it offers so small a sliding angle of a water droplet that itcauses little deformation of a water droplet and has a little differencebetween advancing and receding contact angles.

Although polymer PA used in the resist composition of the invention mayexert satisfactory performance by a combination of repeat units offormulae (1a), (1b), (2a), and (2b), they may also be constructed byfurther combining with repeat units of one or more type of the generalformulae (7a) to (7e), (8a) to (8e), (9a) to (9c), and (10a) to (10c),shown below, for the purposes of imparting additional water repellencyand water slip and controlling alkali solubility and developer affinity.

Herein R¹³ is C₁-C₁₀ alkyl or fluoroalkyl; R¹⁴ is an adhesive group; R¹⁵is an acid labile group; R¹⁶ is a single bond or a divalent C₁-C₁₀organic group; R¹⁷ and R¹⁸ are each hydrogen, methyl or trifluoromethyl.

In formulae (7a) and (8a), exemplary C₁-C₁₀ alkyl groups represented byR¹³ include, but are not limited to, methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-heptyl,n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,cyclohexylbutyl, and adamantyl. Suitable fluoroalkyl groups representedby R¹³ include the above-exemplified alkyl groups in which some or allhydrogen atoms are substituted by fluorine atoms, such as, for example,2,2,2-trifluoroethyl, 3,3,3-trifluoropropyl,1,1,2,2,3,3,3-heptafluoropropyl, 1H,1H,3H-tetrafluoropropyl,1H,1H,5H-octafluoropentyl, 1H,1H,7H-dodecafluoroheptyl,2-(perfluorobutyl)ethyl, 2-(perfluorohexyl)ethyl,2-(perfluorooctyl)ethyl, and 2-(perfluorodecyl)ethyl.

In formulae (7b) and (8b), the adhesive group represented by R¹⁴ may beselected from a variety of such groups, typically those groups shownbelow.

Herein, the broken line designates a valence bond.

In formulae (7c) and (8c), the acid labile group represented by R¹⁵ maybe selected from those groups illustrated for R³.

In formulae (7e), (8e), and (9a) to (9c), suitable divalent organicgroups represented by R¹⁶ include alkylene groups such as methylene andgroups of the following formulae.

Herein, the broken line designates a valence bond.

The polymer PA used in the resist composition may be synthesized bygeneral polymerization processes including radical polymerizataion usinginitiators such as 2,2′-azobisisobutyronitrile (AIBN), and ionic (oranionic) polymerization using alkyllithium or the like. Thepolymerization may be carried out by its standard technique. Preferablythe polymers are prepared by radical polymerization while thepolymerization conditions may be determined in accordance with the typeof initiator, temperature, pressure, concentration, solvent, additives,and the like.

Examples of the radical polymerization initiator used herein include azocompounds such as 2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2,4,4-trimethylpentane), and dimethyl2,2′-azobis(isobutyrate); peroxides such as tert-butylperoxypivalate,lauroyl peroxide, benzoyl peroxide, and tert-butylperoxylaurate;water-soluble polymerization initiators such as potassium persulfate;and redox initiators comprising a peroxide (e.g., potassium persulfateor hydrogen peroxide) combined with a reducing agent (e.g., sodiumsulfite). Although the amount of polymerization initiator used may varywith its type and other polymerization conditions, it is generally usedin an amount of 0.001 to 10 mol %, and preferably 0.01 to 5 mol % basedon the total moles of monomers to be polymerized.

During the synthesis of polymer PA, any known chain transfer agent suchas dodecyl mercaptan or 2-mercaptoethanol may be added for molecularweight control purpose. The amount of chain transfer agent added ispreferably 0.01 to 10 mol % based on the total moles of monomers to bepolymerized.

While polymer PA may be synthesized by combining suitable monomersselected from polymerizable monomers corresponding to repeat units offormulae (1a), (1b), (2a), (2b), (7a) to (7e), (8a) to (8e), (9a) to(9c), and (10a) to (10c), adding an initiator and chain transfer agentto the monomer mixture, and effecting polymerization, a solvent may beused if necessary. Any solvent may be used as long as it does notinterfere with the desired polymerization reaction. Typical solventsused herein include esters such as ethyl acetate, n-butyl acetate, andγ-butyrolactone; ketones such as acetone, methyl ethyl ketone, andmethyl isobutyl ketone; aliphatic or aromatic hydrocarbons such astoluene, xylene and cyclohexane; alcohols such as isopropyl alcohol andethylene glycol monomethyl ether; and ether solvents such as diethylether, dioxane, and tetrahydrofuran, which may be used alone or inadmixture. Although the amount of solvent used may vary with the desireddegree of polymerization (or molecular weight), the amount of initiatoradded, and other polymerization conditions such as polymerizationtemperature, it is generally used in such an amount as to provide aconcentration of 0.1 to 95% by weight, preferably 5 to 90% by weight ofmonomers to be polymerized.

Although the temperature of the polymerization reaction may vary withthe identity of polymerization initiator or the boiling point ofsolvent, it is preferably in the range of 20 to 200° C., and morepreferably 50 to 140° C. Any desired reactor or vessel may be used forthe polymerization reaction.

From the solution or dispersion of the polymer thus synthesized, theorganic solvent or water serving as the reaction medium is removed byany well-known techniques. Suitable techniques include, for example,re-precipitation followed by filtration, and heat distillation undervacuum.

Polymer P2 used herein may be synthesized by synthesizing a polymer P1-Hcomprising repeat units of formulae (1a) and (2a′), then effectingpost-protection reaction to substitute for some or all hydroxyl groups.

Herein, R^(1a), R^(1b), R², a1 and b1 are as defined above.

Polymer P2 is obtainable by reacting polymer P1-H with a base in anamount of 1 to 2 equivalents relative to the desired degree ofsubstitution of hydroxyl groups, and then with R—X (wherein R is an acidlabile group or alkyl as mentioned above and X is chlorine, bromine oriodine) in an amount of 1 to 2 equivalents relative to the base.

The post-protection reaction may be effected in a solvent, which isselected from hydrocarbons such as benzene and toluene, and ethers suchas dibutyl ether, diethylene glycol diethyl ether, diethylene glycoldimethyl ether, tetrahydrofuran and 1,4-dioxane, alone or in admixture.Suitable bases used herein include, but are not limited to, sodiumhydride, n-butyllithium, lithium diisopropylamide, triethylamine, andpyridine.

Desirably polymers PA have a weight average molecular weight (Mw) of1,000 to 500,000, and especially 2,000 to 30,000, as determined by gelpermeation chromatography (GPC) using polystyrene standards. This isbecause a polymer with too low a Mw may be more dissolvable in waterwhereas too high a Mw may interfere with film formation after spincoating and lead to a decline of alkali solubility.

In polymer PA wherein U1 stands for a total molar number of a monomercorresponding to units of formula (1a), U2 stands for a total molarnumber of a monomer corresponding to units of formula (1b), U3 standsfor a total molar number of a monomer corresponding to units of formula(2a), and U4 stands for a total molar number of a monomer correspondingto units of formula (2b), with the proviso that U1+U2+U3+U4=UA, valuesof U1, U2, U3 and U4 are preferably determined so as to meet:

0≦U1/UA<1, more preferably 0.2≦U1/UA≦0.7, even more preferably0.3≦U1/UA≦0.7,

0≦U2/UA<1, more preferably 0.1≦U2/UA≦0.7, even more preferably0.1≦U2/UA≦0.5,

0≦U3/UA<1, more preferably 0.1≦U3/UA≦0.6, even more preferably0.1≦U3/UA≦0.5, and

0≦U4/UA<1, more preferably 0≦U4/UA≦0.7, even more preferably0.1≦U4/UA≦0.5.

In the embodiment wherein additional repeat units of formulae (7a) to(7e), (8a) to (8e), (9a) to (9c), (10a) to (10c) are incorporated intothe polymers for the purpose of improving their function as an additivein the resist composition, provided that U5 stands for a total molarnumber of monomers corresponding to the additional units andU1+U2+U3+U4+U5=UA′, a ratio of UA to UA′ is preferably determined so asto meet 0≦UA/UA′≦1, more preferably 0.6<UA/UA′≦1, and even morepreferably 0.8≦UA/UA′≦1.

In the first embodiment wherein polymer PA is used as an additive toresist material, it is combined with base polymer (B) preferably in suchamounts that the amount of polymer PA is 0.1 to 50 parts, morepreferably 0.5 to 10 parts by weight per 100 parts by weight of polymer(B). At least 0.1 phr of polymer PA is effective in forming aphotoresist film having an increased receding contact angle with wateron its surface. Up to 50 phr of polymer PA ensures to form a photoresistfilm having a low dissolution rate in an alkaline developer, maintainingthe height of a fine pattern formed therefrom.

B. Base Polymer

The resist composition is typically a chemically amplified positiveresist composition. Base polymer (B) to be combined with additivepolymer (A) is a polymer comprising a structure having one or both of alactone ring and a hydroxyl group and/or a maleic anhydride-derivedstructure which becomes soluble in an alkaline developer under theaction of an acid. Suitable polymers or base resins (B) include polymersof (meth)acrylic acid esters, copolymers of (α-trifluoromethyl)acrylateand maleic anhydride, alternating copolymers of cyclolefins and maleicanhydride, polynorbornene, cycloolefin ring-opening metathesispolymerization (ROMP) polymers, hydrogenated cycloolefin ROMP polymers,and the like.

Specifically the polymer (B) used herein includes, but is not limitedto, those polymers comprising units of the following formula (R1) and/or(R2) and having a weight average molecular weight (Mw) of 1,000 to100,000, and especially 3,000 to 30,000, as measured by GPC versuspolystyrene standards.

Herein, R⁰⁰¹ is hydrogen, methyl, trifluoromethyl or —CH₂CO₂R⁰⁰³; R⁰⁰²is hydrogen, methyl or —CO₂R⁰⁰³; R⁰⁰³ is a straight, branched or cyclicC₁-C₁₅ alkyl; R⁰⁰⁴ is hydrogen or a monovalent C₁-C₁₅ hydrocarbon grouphaving a fluorinated substituent group, carboxyl group or hydroxylgroup; at least one of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent C₁-C₁₅hydrocarbon group having a fluorinated substituent group, carboxyl groupor hydroxyl group while the remaining R's independently representhydrogen or straight, branched or cyclic C₁-C₁₅ alkyl groups; R⁰⁰⁹ is amonovalent C₃-C₁₅ hydrocarbon group containing a —CO₂— partialstructure; at least one of R⁰¹⁰ to R⁰¹³ is a monovalent C₂-C₁₅hydrocarbon group containing a —CO₂— partial structure, while theremaining R's are independently hydrogen or straight, branched orcyclic, C₁-C₁₅ alkyl groups; R⁰¹⁴ is a polycyclic C₇-C₁₅ hydrocarbongroup or an alkyl group containing such a polycyclic hydrocarbon group;R⁰¹⁵ is an acid labile group; X is methylene or oxygen; R⁰¹⁶ and R⁰¹⁸are hydrogen or methyl; R⁰¹⁷ is straight, branched or cyclic C₁-C_(B)alkyl; and k is 0 or 1. In formula (R1), the subscripts a1′, a2′, a3′,b1′, b2′, b3′, c1′, c2′, c3′, d1′, d2′, d3′, and e′ are numbers from 0to less than 1, satisfyinga1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1. In formula (R2),f′, g′, h′, i′, j′, k′, l′, m′ and n′ are numbers from 0 to less than 1,satisfying f′+g′+h′+i′+j′+k′+l′+m′+n′=1; x′, y′ and z′ are each aninteger of 0 to 3, satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3.

Examples of R⁰⁰³ include methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl,cyclohexyl, ethylcyclopentyl, butylcyclopentyl, ethylcyclohexyl,butylcyclohexyl, adamantyl, ethyladamantyl, and butyladamantyl.

Examples of the hydrocarbon group represented by R⁰⁰⁴ includecarboxyethyl, carboxybutyl, carboxycyclopentyl, carboxycyclohexyl,carboxynorbornyl, carboxyadamantyl, hydroxyethyl, hydroxybutyl,hydroxycyclopentyl, hydroxycyclohexyl, hydroxynorbornyl,hydroxyadamantyl, hydroxyhexafluoroisopropylcyclohexyl, anddi(hydroxyhexafluoroisopropyl)cyclohexyl.

R⁰⁰⁵ to R⁰⁰⁸ denote monovalent C₁-C₁₅ hydrocarbon groups having afluorinated substituent group, carboxyl group or hydroxyl group,examples of which include carboxy, carboxymethyl, carboxyethyl,carboxybutyl, hydroxymethyl, hydroxyethyl, hydroxybutyl,2-carboxyethoxycarbonyl, 4-carboxybutoxycarbonyl,2-hydroxyethoxycarbonyl, 4-hydroxybutoxycarbonyl,carboxycyclopentyloxycarbonyl, carboxycyclohexyloxycarbonyl,carboxynorbornyloxycarbonyl, carboxyadamantyloxycarbonyl,hydroxycyclopentyloxycarbonyl, hydroxycyclohexyloxycarbonyl,hydroxynorbornyloxycarbonyl, hydroxyadamantyloxycarbonyl,hydroxyhexafluoroisopropylcyclohexyloxycarbonyl, anddi(hydroxyhexafluoroisopropyl)cyclohexyloxycarbonyl. Examples of thestraight, branched or cyclic C₁-C₁₅ alkyl group are the same asexemplified for R⁰⁰³. Alternatively, two of R⁰⁰⁵ to R⁰⁰⁸ (e.g., R⁰⁰⁵ andR⁰⁰⁶, R⁰⁰⁶ and R⁰⁰⁷) may bond together to form a ring with the carbonatom(s) to which they are attached. In that event, at least one ofring-forming R⁰⁰⁵ to R⁰⁰⁸ is a divalent C₁-C₁₅ hydrocarbon group havinga fluorinated substituent group, carboxyl group or hydroxyl group, whilethe remaining are independently a single bond or a straight, branched orcyclic C₁-C₁₅ alkylene group. Examples of the divalent C₁-C₁₅hydrocarbon group having a fluorinated substituent group, carboxyl groupor hydroxyl group include the groups exemplified as the monovalenthydrocarbon group having a fluorinated substituent group, carboxyl groupor hydroxyl group, with one hydrogen atom eliminated therefrom. Examplesof the straight, branched or cyclic C₁-C₁₅ alkylene groups include thegroups exemplified for R⁰⁰³, with one hydrogen atom eliminatedtherefrom.

Examples of the monovalent C₃-C₁₅ hydrocarbon group containing a —CO₂—partial structure, represented by R⁰⁰⁹, include 2-oxooxolan-3-yl,4,4-dimethyl-2-oxooxolan-3-yl, 4-methyl-2-oxooxan-4-yl,2-oxo-1,3-dioxolan-4-ylmethyl, and 5-methyl-2-oxooxolan-5-yl.

Examples of the monovalent C₂-C₁₅ hydrocarbon group containing a —CO₂—partial structure, represented by R⁰¹⁰ to R⁰¹³, include2-oxooxolan-3-yloxycarbonyl, 4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branchedor cyclic C₁-C₁₅ alkyl groups are the same as exemplified for R⁰⁰³.Alternatively, two of R⁰¹⁰ to R⁰¹³ (e.g., R⁰¹⁰ and R⁰¹¹, R⁰¹¹ and R⁰¹²)may bond together to form a ring with the carbon atom(s) to which theyare attached. In that event, at least one of ring-forming R⁰¹⁰ to R⁰¹³is a divalent C₂-C₁₅ hydrocarbon group containing a —CO₂— partialstructure, while the remaining are independently a single bond or astraight, branched or cyclic C₁-C₁₅ alkylene group. Examples of thedivalent C₁-C₁₅ hydrocarbon group containing a —CO₂— partial structureinclude 1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as wellas the groups exemplified as the monovalent hydrocarbon group containinga —CO₂— partial structure, with one hydrogen atom eliminated therefrom.Examples of the straight, branched or cyclic C₁-C₁₅ alkylene groupsinclude the groups exemplified for R⁰⁰³, with one hydrogen atomeliminated therefrom.

Examples of the polycyclic C₇-C₁₅ hydrocarbon group or the alkyl groupcontaining such a polycyclic hydrocarbon group, represented by R⁰¹⁴,include norbornyl, bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl,adamantyl, ethyladamantyl, butyladamantyl, norbornylmethyl, andadamantylmethyl.

The acid labile groups represented by R⁰¹⁵ may be selected from avariety of such groups. Examples of the acid labile group are groups ofthe general formulae (L1) to (L4), tertiary alkyl groups of 4 to 20carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groups inwhich each alkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groups of4 to 20 carbon atoms. Examples are the same as illustrated for the acidlabile group R³ in formula (2a).

Additionally, any of indene, norbornadiene, acenaphthylene, and vinylether monomers may be copolymerized in the polymers of formulae (R1) and(R2).

Examples of the repeat units incorporated at compositional ratio a1′ informula (R1) are shown below, though not limited thereto.

Examples of the repeat units incorporated at compositional ratio b1′ informula (R1) are shown below, though not limited thereto.

Examples of the repeat units incorporated at compositional ratio d1′ informula (R1) are shown below, though not limited thereto.

Examples of the repeat units incorporated at compositional ratio a3′,b3′, c3′ and d3′ in formula (R1) are shown below, though not limitedthereto.

Among polymers of formula (R1), exemplary(α-trifluoromethyl)acrylate/maleic anhydride copolymers andcycloolefin/maleic anhydride copolymers are shown below, though theuseful polymers are not limited thereto.

Furthermore, repeat units having a photosensitive sulfonium salt asrepresented by the following general formula may be copolymerized with(R1) and/or (R2) and incorporated in the polymers.

Herein R^(p1) is hydrogen or methyl. R^(p2) is phenylene, —O—R^(p5)— or—C(═O)—X—R^(p5)— wherein X is an oxygen atom or NH, and R^(p5) is astraight, branched or cyclic C₁-C₆ alkylene, alkenylene or phenylenegroup which may contain a carbonyl, ester or ether group. R^(p3) andR^(p4) are each independently a straight, branched or cyclic C₁-C₁₂alkyl group which may contain a carbonyl, ester or ether group, or aC₆-C₁₂ aryl group, C₁-C₂₀ aralkyl group or thiophenyl group. X⁻ is anon-nucleophilic counter ion.

The polymer used as the base resin (B) is not limited to one type and amixture of two or more polymers may be added. The use of plural polymersallows for easy adjustment of resist properties.

C. Acid Generator

In the resist composition of the invention, an acid generator,specifically a compound capable of generating an acid in response tohigh-energy radiation may be included in order that the resistcomposition function as a chemically amplified positive resistcomposition. The acid generator may be any compound capable ofgenerating an acid upon exposure of high-energy radiation, which isgenerally referred to as “photoacid generator” or PAG. Suitablephotoacid generators include sulfonium salts, iodonium salts,sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acidgenerators. Exemplary acid generators are given below while they may beused alone or in admixture of two or more. The acid generators usedherein are not limited to those exemplified below.

Sulfonium salts are salts of sulfonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary sulfonium cations includetriphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium,tribenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium,2-oxo-2-phenylethylthiacyclopentanium,4-n-butoxynaphthyl-1-thiacyclopentanium, and2-n-butoxynaphthyl-1-thiacyclopentanium.

Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4′-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Sulfonium salts based on combinationof the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary iodonium cations are aryliodoniumcations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.

Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Iodonium salts based on combinationof the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonyl-carbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,bis(4-acetyloxyphenylsulfonyl)diazomethane,bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane,bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)-diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imideskeletons with sulfonates. Exemplary imide skeletons are succinimide,naphthalene dicarboxylic acid imide, phthalimide, cyclohexyldicarboxylicacid imide, 5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide. Exemplarysulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoinmesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol,phloroglucinol, catechol, resorcinol, and hydroquinone, in which all thehydroxyl groups are substituted by trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzylsulfonate, 2-nitrobenzyl sulfonate, and 2,6-dinitrobenzyl sulfonate,with exemplary sulfonates including trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropane-sulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Also useful are analogous nitrobenzyl sulfonate compounds in which thenitro group on the benzyl side is substituted by a trifluoromethylgroup.

Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Photoacid generators in the form of glyoxime derivatives are describedin Japanese Patent No. 2,906,999 and JP-A 9-301948 and includebis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(10-camphorsulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-nioxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-nioxime,bis-O-(10-camphorsulfonyl)-nioxime, bis-O-(benzenesulfonyl)-nioxime,bis-O-(p-fluorobenzenesulfonyl)-nioxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-nioxime, andbis-O-(xylenesulfonyl)-nioxime.

Also included are the oxime sulfonates described in U.S. Pat. No.6,004,724, for example,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenyl-acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenyl-acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenyl-acetonitrile,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,etc.

Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,(5-(4-(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrileand(5-(2,5-bis(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile.

Also included are the oxime sulfonates described in U.S. Pat. No.6,261,738 and JP-A 2000-314956, for example,2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphoryl-sulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(4-methoxyphenylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanoneoxime-O-(2,4,6-trimethylphenylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(methylsulfonate);2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanoneoxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-10-camphorylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(1-naphthyl)-sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2,4,6-trimethylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methyl-sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethyl-phenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-dodecylphenyl)-sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethyl-phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(4-dodecylphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethyl-phenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate;2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate;2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanoneoxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-methyl-sulfonate;2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanoneoxime-O-propylsulfonate;1,3-bis[1-(4-phenoxyphenyl)-2,2,2-trifluoro-ethanoneoxime-O-sulfonyl]phenyl;2,2,2-trifluoro-1-[4-methylsulfonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylcarbonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methoxycarbonylmethoxyphenyl]-ethanoneoxime-O-propyl-sulfonate;2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzyloxy-phenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[2-thiophenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(trifluoromethanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(trifluoromethanesulfonate);2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-propane-sulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-propanesulfonate); and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-butanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-butanesulfonate).

Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(4-(4-methyl-phenylsulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(4-(4-methylphenylsulfonyloxy)-phenylsulfonate) and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonyloxy-imino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)-phenylsulfonate).

Also included are the oxime sulfonates described in JP-A 9-95479 andJP-A 9-230588 and the references cited therein, for example,α-(p-toluenesulfonyloxyimino)-phenylacetonitrile,α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile,α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylaceto-nitrile,α-(benzenesulfonyloxyimino)-2-thienylacetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile,α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-3-thienylacetonitrile,α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, andα-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Also included are oxime sulfonates having the formula:

wherein R^(s1) is a substituted or unsubstituted haloalkylsulfonyl orhalobenzenesulfonyl group of 1 to 10 carbon atoms, R^(s2) is a haloalkylgroup of 1 to 11 carbon atoms, and Ar^(s1) is substituted orunsubstituted aromatic or hetero-aromatic group, as described in WO2004/074242.Examples include2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluoro-butylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-fluorene,2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-fluorene,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxy-imino)-pentyl]-4-biphenyl,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-4-biphenyl,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-4-biphenyl.

Suitable bisoxime sulfonates include those described in JP-A 9-208554,for example,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediaceto-nitrile,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediaceto-nitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediaceto-nitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediaceto-nitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediaceto-nitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediaceto-nitrile,etc.

Of these, preferred photoacid generators are sulfonium salts,bissulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonates andglyoxime derivatives. More preferred photoacid generators are sulfoniumsalts, bissulfonyldiazomethanes, N-sulfonyloxyimides, andoxime-O-sulfonates. Typical examples include triphenylsulfoniump-toluenesulfonate, triphenylsulfonium camphorsulfonate,triphenylsulfonium pentafluorobenzenesulfonate, triphenylsulfoniumnonafluorobutanesulfonate, triphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniump-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniumcamphorsulfonate, 4-tert-butoxyphenyldiphenylsulfonium4-(4′-toluenesulfonyl-oxy)benzenesulfonate,tris(4-methylphenyl)sulfonium camphorsulfonate,tris(4-tert-butylphenyl)sulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium nonafluoro-1-butane-sulfonate,4-tert-butylphenyldiphenylsulfoniumpentafluoroethyl-perfluorocyclohexanesulfonate,4-tert-butylphenyldiphenylsulfonium perfluoro-1-octane-sulfonate,triphenylsulfonium 1,1-difluoro-2-naphthyl-ethanesulfonate,triphenylsulfonium1,1,2,2-tetrafluoro-2-(norbornan-2-yl)-ethanesulfonate,bis(tert-butylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(4-tert-butylphenylsulfonyl)diazomethane,N-camphorsulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,N-p-toluenesulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxy-imino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-fluorene,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-fluorene.

In the chemically amplified positive resist composition, an appropriateamount of the photoacid generator is, but not limited to, 0.1 to 20parts, and especially 0.1 to 10 parts by weight per 100 parts by weightof the base resin (B). If the amount of the PAG is up to 20 phr, theresulting photoresist film has a sufficiently high transmittance tominimize a risk of degrading resolution. The PAG may be used alone or inadmixture of two or more. The transmittance of the resist film can becontrolled by using a PAG having a low transmittance at the exposurewavelength and adjusting the amount of the PAG added.

In the resist composition, there may be added a compound which isdecomposed with an acid to generate another acid, that is,acid-amplifier compound. For these compounds, reference should be madeto J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9,29-30 (1996).

Examples of the acid-amplifier compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto.Of well-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior.

In the resist composition, an appropriate amount of the acid-amplifiercompound is up to 2 parts, and preferably up to 1 part by weight per 100parts by weight of the base resin (B). Up to 2 phr of the acid-amplifiercompound allows for diffusion control, minimizing a risk of degradingresolution and pattern profile.

In addition to (A) additive polymer, (B) base resin or polymer and (C)photoacid generator, the resist composition of the invention may furthercomprise (D) an organic solvent, (E) a basic compound, and (F) adissolution inhibitor.

D. Solvent

The organic solvent used herein may be any organic solvent in which theadditive polymer, base resin, acid generator, and other components aresoluble. Illustrative, non-limiting, examples of the organic solventinclude ketones such as cyclohexanone and methyl-2-n-amyl ketone;alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol,1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propyleneglycol monomethyl ether, ethylene glycol monomethyl ether, propyleneglycol monoethyl ether, ethylene glycol monoethyl ether, propyleneglycol dimethyl ether, and diethylene glycol dimethyl ether; esters suchas propylene glycol monomethyl ether acetate (PGMEA), propylene glycolmonoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate,methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butylacetate, tert-butyl propionate, and propylene glycol mono-tert-butylether acetate; and lactones such as γ-butyrolactone. These solvents maybe used alone or in combinations of two or more thereof. Of the aboveorganic solvents, it is recommended to use diethylene glycol dimethylether, 1-ethoxy-2-propanol, PGMEA, and mixtures thereof because the acidgenerator is most soluble therein.

An appropriate amount of the organic solvent used is 200 to 3,000 parts,especially 400 to 2,500 parts by weight per 100 parts by weight of thebase resin (B).

E. Basic Compound

In the resist composition, an organic nitrogen-containing compound orcompounds may be compounded as the basic compound. The organicnitrogen-containing compound used herein is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe acid generator diffuses within the resist film. The inclusion oforganic nitrogen-containing compound holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure andreduces substrate and environment dependence, as well as improving theexposure latitude and the pattern profile.

Suitable organic nitrogen-containing compounds include, but are notlimited to, primary, secondary, and tertiary aliphatic amines, mixedamines, aromatic amines, heterocyclic amines, nitrogen-containingcompounds having carboxyl group, nitrogen-containing compounds havingsulfonyl group, nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, amidederivatives, imide derivatives, and carbamate derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, anddimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives,pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives,piperidine derivatives, piperazine derivatives, morpholine derivatives,indole derivatives, isoindole derivatives, 1H-indazole derivatives,indoline derivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl or hydroxyphenylgroup include 2-hydroxypyridine, aminocresol, 2,4-quinolinediol,3-indolemethanol hydrate, monoethanolamine, diethanolamine,triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine,triisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol,3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide,benzamide, and 1-cyclohexylpyrrolidone. Suitable imide derivativesinclude phthalimide, succinimide, and maleimide. Suitable carbamatederivatives include N-t-butoxycarbonyl-N,N-dicyclohexylamine,N-t-butoxycarbonylbenzimidazole and oxazolidinone.

In addition, organic nitrogen-containing compounds of the followinggeneral formula (B)-1 may also be included alone or in admixture.

N(X)_(n)(Y)_(3-n)   (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain an ether or hydroxyl group; and side chain X is independentlyselected from groups of the following general formulas (X1) to (X3), andtwo or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched C₁-C₄ alkylene groups; R³⁰¹ and R³⁰⁴ are independently hydrogenor a straight, branched or cyclic C₁-C₂₀ alkyl group which may containone or more hydroxyl, ether, ester groups or lactone rings; R³⁰³ is asingle bond or a straight or branched C₁-C₄ alkylene group; and R³⁰⁶ isa straight, branched or cyclic C₁-C₂₀ alkyl group which may contain oneor more hydroxyl, ether, ester groups or lactone rings.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane,1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6,tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine,tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine,tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine,tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)-ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)-ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

Also useful are one or more organic nitrogen-containing compounds havingcyclic structure represented by the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched C₂-C₂₀alkylene group which may contain one or more carbonyl, ether, ester orsulfide groups.

Illustrative examples of the organic nitrogen-containing compoundshaving formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethylmorpholinoacetate, 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl2-(2-methoxyethoxy)acetate, 2-morpholinoethyl2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate,2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate,2-morpholinoethyl laurate, 2-morpholinoethyl myristate,2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also, one or more organic nitrogen-containing compounds having cyanogroup represented by the following general formulae (B)-3 to (B)-6 maybe blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched C₁-C₄ alkylene group.

Illustrative examples of the organic nitrogen-containing compoundshaving cyano represented by formulae (B)-3 to (B)-6 include3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiono-nitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiono-nitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-amino-propionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

Also included are organic nitrogen-containing compounds of imidazolestructure having a polar functional group, represented by the generalformula (B)-7.

Herein, R³¹⁰ is a straight, branched or cyclic alkyl group of 2 to 20carbon atoms bearing at least one polar functional group selected fromamong hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano andacetal groups; R³¹¹, R³¹² and R³¹³ are each independently hydrogen, astraight, branched or cyclic alkyl group, aryl group or aralkyl grouphaving 1 to 10 carbon atoms.

Also included are organic nitrogen-containing compounds of benzimidazolestructure having a polar functional group, represented by the generalformula (B)-8.

Herein, R³¹⁴ is hydrogen, a straight, branched or cyclic alkyl group,aryl group or aralkyl group having 1 to 10 carbon atoms. R³¹⁵ is a polarfunctional group-bearing, straight, branched or cyclic C₁-C₂₀ alkylgroup, and the alkyl group contains as the polar functional group atleast one group selected from among ester, acetal and cyano groups, andmay additionally contain at least one group selected from amonghydroxyl, carbonyl, ether, sulfide and carbonate groups.

Further included are heterocyclic nitrogen-containing compounds having apolar functional group, represented by the general formulae (B)-9 and(B)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or≡C—R³²³, R³¹⁶ is a straight, branched or cyclic alkyl group of 2 to 20carbon atoms bearing at least one polar functional group selected fromamong hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano andacetal groups; R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independentlyhydrogen, a straight, branched or cyclic alkyl group or aryl grouphaving 1 to 10 carbon atoms, or a pair of R³¹⁷ and R³¹⁸ and a pair ofR³¹⁹ and R³²⁰, taken together, may form a benzene, naphthalene orpyridine ring with the carbon atoms to which they are attached; R³²¹ ishydrogen, a straight, branched or cyclic alkyl group or aryl grouphaving 1 to 10 carbon atoms; R³²² and R³²³ each are hydrogen, astraight, branched or cyclic alkyl group or aryl group having 1 to 10carbon atoms, or a pair of R³²¹ and R³²³, taken together, may form abenzene or naphthalene ring with the carbon atoms to which they areattached.

Also included are organic nitrogen-containing compounds of aromaticcarboxylic ester structure having the general formulae (B)-11 to (B)-14.

Herein R³²⁴ is a C₆-C₂₀ aryl group or C₄-C₂₀ hetero-aromatic group, inwhich some or all hydrogen atoms may be replaced by halogen atoms,straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups,C₇-C₂₀ aralkyl groups, C₁-C₁₀ alkoxy groups, C₁-C₁₀ acyloxy groups orC₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ isa C₁-C₁₀ alkyl group, in which some methylene groups may be replaced byoxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which somemethylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond,methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is anitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogenatom or CR³³². R³³⁰, R³³¹ and R³³² are each independently hydrogen,methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair ofR³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀hetero-aromatic ring with the carbon atoms to which they are attached.

Further included are organic nitrogen-containing compounds of7-oxanorbornane-2-carboxylic ester structure having the general formula(B)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkylgroup. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀aryl group or C₁-C₂₀ aralkyl group, which may contain one or more polarfunctional groups selected from among ether, carbonyl, ester, alcohol,sulfide, nitrile, amine, imine, and amide and in which some hydrogenatoms may be replaced by halogen atoms. R³³⁴ and R³³⁵, taken together,may form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atomswith the nitrogen atom to which they are attached.

The organic nitrogen-containing compounds may be used alone or inadmixture of two or more. The organic nitrogen-containing compound ispreferably formulated in an amount of 0.001 to 2 parts, and especially0.01 to 1 part by weight, per 100 parts by weight of the base resin (B).At least 0.001 phr of the nitrogen-containing compound achieves adesired addition effect whereas up to 2 phr minimizes a risk of loweringsensitivity.

F. Dissolution Inhibitor

The dissolution inhibitor which can be added to the resist compositionis a compound having on the molecule at least two phenolic hydroxylgroups, in which an average of from 0 to 100 mol % of all the hydrogenatoms on the phenolic hydroxyl groups are replaced by acid labile groupsor a compound having on the molecule at least one carboxyl group, inwhich an average of 50 to 100 mol % of all the hydrogen atoms on thecarboxyl groups are replaced by acid labile groups, both the compoundshaving a weight average molecular weight within a range of 100 to 1,000,and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having a carboxyl group include those offormulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl group; R²⁰³ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl group, or —(R²⁰⁷)_(h)—COOH; R²⁰⁴ is—(CH₂)_(i)—, C₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or asulfur atom; R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶ is hydrogen, a straightor branched C₁-C₈ alkyl or alkenyl, or a phenyl or naphthyl group inwhich at least one hydrogen atom is substituted by a hydroxyl group;R²⁰⁷ is a straight or branched C₁-C₁₀ alkylene; R²⁰⁸ is hydrogen orhydroxyl; h is 0 or 1, i is an integer of 2 to 10, j is an integer of 0to 5, u is 0 or 1; s, t, s′, t′, s″, and t″ are each numbers whichsatisfy s+t=8, s′+t′=5, and s″+t″=4, and are such that each phenylstructure has at least one hydroxyl group; and α is a number such thatthe compounds of formula (D8) or (D9) have a weight average molecularweight of from 100 to 1,000.

Exemplary acid labile groups on the dissolution inhibitor include avariety of such groups, typically groups of the general formulae (L1) to(L4), tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups in which eachof the alkyls has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkyl groups.Examples of the respective groups are as previously described.

The dissolution inhibitor may be formulated in an amount of 0 to 50parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts byweight, per 100 parts by weight of the base resin (B), and may be usedsingly or as a mixture of two or more thereof. Up to 50 parts of thedissolution inhibitor may minimize a risk of slimming the patterned filmto invite a decline in resolution.

The dissolution inhibitor can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

If desired, the resist composition of the invention may further comprisea carboxylic acid compound, acetylene alcohol derivative or otheroptional ingredients. Optional ingredients may be added in conventionalamounts so long as this does not compromise the objects of theinvention.

The carboxylic acid compound used herein may be one or more compoundsselected from Groups I and II below, but is not limited thereto.Including this compound improves the post-exposure delay (PED) stabilityof the resist and ameliorates edge roughness on nitride film substrates.

Group I:

Compounds of general formulas (A1) to (A10) below in which some or allof the hydrogen atoms on the phenolic hydroxyl groups are replaced by—R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight or branched C₁-C₁₀ alkylenegroup), and in which the molar ratio C/(C+D) of phenolic hydroxyl groups(C) to ≡C—COOH groups (D) in the molecule is from 0.1 to 1.0.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰² and R⁴⁰³ are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl. R⁴⁰⁴ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or a —(R⁴⁰⁹)_(h)—COOR′ group wherein R′is hydrogen or —R⁴⁰⁹—COOH. R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom.R⁴⁰⁶ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom. R⁴⁰⁷ is hydrogen, a straight or branchedC₁-C₈ alkyl or alkenyl, or a hydroxyl-substituted phenyl or naphthyl.R⁴⁰⁸ is hydrogen or methyl. R⁴⁰⁹ is a straight or branched C₁-C₁₀alkylene. R⁴¹⁰ is hydrogen, a straight or branched C₁-C₈ alkyl oralkenyl, or a —R⁴¹¹—COOH group wherein R⁴¹¹ is a straight or branchedC₁-C₁₀ alkylene. R⁴¹² is hydrogen or hydroxyl. The letter j is a numberfrom 0 to 3; s1, t1, s2, t2, s3, t3, s4, and t4 are each numbers whichsatisfy s1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6, and are such that eachphenyl structure has at least one hydroxyl group; s5 and t5 are numberswhich satisfy s5≧0, t5≧0, and s5+t5=5; u is a number from 1 to 4; h is anumber from 1 to 4; κ is a number such that the compound of formula (A6)may have a weight average molecular weight of 1,000 to 5,000; and λ is anumber such that the compound of formula (A7) may have a weight averagemolecular weight of 1,000 to 10,000.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κand λ are as defined above.

The compound having a ≡C—COOH group may be used singly or ascombinations of two or more thereof. The compound having a ≡C—COOH groupis added in an amount ranging from 0 to 5 parts, preferably 0.1 to 5parts, more preferably 0.1 to 3 parts, and further preferably 0.1 to 2parts by weight, per 100 parts by weight of the base polymer (B). Up to5 phr of the compound may have a minimal risk of reducing the resolutionof the resist composition.

Preferred examples of the acetylene alcohol derivative which can beadded to the resist composition include those having the general formula(S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or astraight, branched or cyclic C₁-C₈ alkyl; and X and Y are each 0 or apositive number, satisfying 0≦X≦30, 0≦Y≦30, and 0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industries Ltd.

The acetylene alcohol derivative is preferably added in an amount of0.01 to 2%, and more preferably 0.02 to 1% by weight based on the resistcomposition. At least 0.01 wt % of the acetylene alcohol derivative iseffective for improving the coating characteristics and shelf stabilitywhereas up to 2 wt % may have little impact on the resolution of theresist composition.

The resist composition of the invention may include optionalingredients, for example, a surfactant which is commonly used forimproving the coating characteristics. Optional ingredients may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Fluorad FC-430 and FC-431from Sumitomo 3M, Ltd., Surflon S-141, S-145, KH-10, KH-20, KH-30 andKH-40 from Asahi Glass Co., Ltd., Unidyne DS-401, DS-403 and DS-451 fromDaikin Industry Co., Ltd., Megaface F-8151 from DIC Corp., and X-70-092and X-70-093 from Shin-Etsu Chemical Co., Ltd. Preferred surfactants areFluorad FC-430 from Sumitomo 3M, Ltd., KH-20 and KH-30 from Asahi GlassCo., Ltd., and X-70-093 from Shin-Etsu Chemical Co., Ltd.

Process

It is now described how to form a pattern using the resist compositionof the invention. A pattern may be formed from the resist composition ofthe invention using any well-known lithography process. The preferredmethod includes at least the steps of forming a photoresist coating on asubstrate, exposing it to high-energy radiation, and developing it witha developer.

For example, the resist composition is applied onto a substrate,typically a silicon wafer by a suitable coating technique such as spincoating. The coating is prebaked on a hot plate at a temperature of 60to 150° C. for 1 to 10 minutes, preferably 80 to 140° C. for 1 to 5minutes, to form a resist film of 0.1 to 2.0 μm thick. It is noted inconjunction with spin coating that if the resist composition is coatedonto the surface of a substrate which has been wetted with the resistsolvent or a solution miscible with the resist solvent, then the amountof the resist composition dispensed can be reduced (see JP-A 9-246173).

A patterning mask having the desired pattern is then placed over thephotoresist film, and the film exposed through the mask to an electronbeam or to high-energy radiation such as deep-UV, excimer laser or x-rayin a dose of 1 to 200 mJ/cm², and preferably 10 to 100 mJ/cm². Thehigh-energy radiation used herein preferably has a wavelength in therange of 180 to 250 nm.

Light exposure may be dry exposure in air or nitrogen atmosphere, EB orEUV exposure in vacuum, or immersion lithography of providing a liquid,typically water between the photoresist film and the projection lens.

The immersion lithography involves prebaking a resist film and exposingthe resist film to light through a projection lens, with deionized wateror similar liquid interposed between the resist film and the projectionlens. Since this allows projection lenses to be designed to a NA of 1.0or higher, formation of finer patterns is possible. The immersionlithography is important for the ArF lithography to survive to the 45-nmnode. The liquid used herein may be a liquid with a refractive index ofat least 1 which is highly transparent at the exposure wavelength,typically deionized water or alkane.

The photoresist film formed from the resist composition of the inventionhas such barrier properties to water that it may inhibit resistcomponents from being leached out in water and as a consequence,eliminate a need for a protective coating in immersion lithography andreduce the cost associated with protective coating formation or thelike. The photoresist film has so high a receding contact angle withwater that few liquid droplets may be left on the surface of thephotoresist film after immersion lithography scanning, minimizingpattern formation failures induced by liquid droplets left on the filmsurface.

In another version of immersion lithography, a protective coating may beformed on top of the resist film. The resist protective coatingsgenerally include solvent-strippable type and developer-soluble typecoatings. A protective coating of the developer-soluble type isadvantageous for process simplification in that it can be strippedduring development of the photoresist film.

The resist protective coating used in the immersion lithography may beformed from a coating solution, for example, a solution of a polymerhaving acidic units such as 1,1,1,3,3,3-hexafluoro-2-propanol residues,carboxyl or sulfo groups which is insoluble in water and soluble in analkaline developer liquid, in a solvent selected from alcohols of atleast 4 carbon atoms, ethers of 8 to 12 carbon atoms, and mixturesthereof. The resist protective coating is not limited thereto.

The resist protective coating may be formed by spin coating a topcoatsolution onto a prebaked photoresist film, and prebaking on a hot plateat 50 to 150° C. for 1 to 10 minutes, preferably at 70 to 140° C. for 1to 5 minutes. Preferably the protective coating has a thickness in therange of 10 to 500 nm. As in the case of resist compositions, the amountof the protective coating material dispensed in forming a protectivecoating by spin coating may be reduced by previously wetting the resistfilm surface with a suitable solvent and applying the protective coatingmaterial thereto.

After exposure to high-energy radiation through a photomask, the resistfilm is post-exposure baked (PEB) on a hot plate at 60 to 150° C. for 1to 5 minutes, and preferably at 80 to 140° C. for 1 to 3 minutes.

Where a resist protective coating is used, sometimes water is left onthe protective coating prior to PEB. If PEB is performed in the presenceof residual water, water can penetrate through the protective coating tosuck up the acid in the resist during PEB, impeding pattern formation.To fully remove the water on the protective coating prior to PEB, thewater on the protective coating should be dried or recovered by suitablemeans, for example, spin drying, purging the protective coating surfacewith dry air or nitrogen, or optimizing the shape of a water recoverynozzle on the relevant stage or a water recovery process.

After exposure, development is carried out using as the developer anaqueous alkaline solution, such as a 0.1 to 5 wt %, preferably 2 to 3 wt%, aqueous solution of tetramethylammonium hydroxide (TMAH), this beingdone by a conventional method such as dip, puddle, or spray developmentfor a period of 10 to 300 seconds, and preferably 0.5 to 2 minutes. Atypical developer is a 2.38 wt % TMAH aqueous solution. These stepsresult in the formation of the desired pattern on the substrate.

Where polymer (A) is used as an additive to a resist material for usewith mask blanks, a resist solution is prepared by adding polymer (A) toany one of the aforementioned base resins. The resist solution is coatedon a mask blank substrate of SiO₂, Cr, CrO, CrN, MoSi or the like. Byfurther forming a SOG film and an organic undercoat film between thephotoresist and the blank substrate, there is provided a three-layerstructure which is also acceptable herein.

As the base resin of the resist composition for use with mask blanks,novolac resins and hydroxystyrene are often used. Those resins in whichalkali soluble hydroxyl groups are substituted by acid labile groups areused for positive resists while these resins in combination withcrosslinking agents are used for negative resists. Base polymers whichcan be used herein include copolymers of hydroxystyrene with one or moreof (meth)acrylic derivatives, styrene, vinyl naphthalene, vinylanthracene, vinyl pyrene, hydroxyvinyl naphthalene, hydroxyvinylanthracene, indene, hydroxyindene, acenaphthylene, and norbornadiene.

Once the resist coating is formed, the structure is exposed to EB invacuum using an EB image-writing system. The exposure is followed bypost-exposure baking (PEB) and development in an alkaline developer for10 to 300 seconds.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. The abbreviations used herein are GPC for gelpermeation chromatography, NMR for nuclear magnetic resonance, Mw forweight average molecular weight, Mn for number average molecular weight,and Mw/Mn for molecular weight dispersity. Mw and Mn are determined byGPC versus polystyrene standards.

Polymer Synthesis Example

Monomers 1 to 10 used in Polymer Synthesis Examples are identified belowby their structural formula.

Polymer Synthesis Example 1

Copolymerization of Monomers 1, 2 and 6 (40/30/30)

To a flask in a nitrogen blanket, 45.94 g of Monomer 1, 19.30 g ofMonomer 2, 35.55 g of Monomer 6, and 42.9 g of γ-butyrolactone were fedto form a monomer solution, which was kept at a temperature of 20-25° C.With stirring, the solution was heated to 60° C., whereupon 4.51 g ofdimethyl 2,2′-azobis(isobutyrate) was added. The polymerization solutionwas continuously stirred for 24 hours while keeping the temperature at60° C. At the end of maturing, the solution was cooled to roomtemperature. To the polymerization solution thus obtained, 300 g ofdiisopropyl ether and 300 g of ultra-pure water were added, followed by15 minutes of stirring. The water layer was discarded, and the organiclayer was washed three times with 300 g of water. The organic layer wasconcentrated and added dropwise to 1,500 g of hexane. The precipitatedcopolymer was separated and washed twice with 600 g of hexane, whereuponwhite solids were isolated. The white solids were vacuum dried at 50° C.for 24 hours, obtaining 53.6 g of the target polymer, Polymer 1. Theresin was analyzed for composition by ¹H-NMR, finding that the copolymerconsisted of Monomers 1, 2 and 6 in a ratio of 53/29/18 mol %. Thecopolymer was also analyzed for molecular weight by GPC, finding Mw of7,100 and Mw/Mn of 1.4.

Polymer Synthesis Examples 2 to 6

Like Polymer 1, Polymers 2 to 6 were synthesized in accordance with theformulation shown in Table 1 and analyzed by GPC. The results are shownin Table 1.

TABLE 1 Monomer (mol%) 1 2 3 4 5 6 7 8 Mw Mw/Mn Polymer 1 40 30 30 7,1001.4 2 40 30 30 6,700 1.4 3 70 30 7,500 1.4 4 70 30 7,600 1.4 5 40 30 307,200 1.4 6 50 20 30 7,300 1.4

Polymer Synthesis Example 7 Copolymerization of Monomers 1 and 6 (70/30)and Post-Protection Reaction

To a flask in a nitrogen blanket, 73.28 g of Monomer 1, 30.42 g ofMonomer 6, and 42.9 g of γ-butyrolactone were fed to form a monomersolution, which was kept at a temperature of 20-25° C. With stirring,the solution was heated to 60° C., whereupon 3.47 g of dimethyl2,2′-azobis-(isobutyrate) was added. The polymerization solution wascontinuously stirred for 24 hours while keeping the temperature at 60°C. At the end of maturing, the solution was cooled to room temperature.To the polymerization solution thus obtained, 300 g of diisopropyl etherand 300 g of ultra-pure water were added, followed by 15 minutes ofstirring. The water layer was discarded, and the organic layer waswashed three times with 300 g of water. The organic layer wasconcentrated and added dropwise to 1,500 g of hexane. The precipitatedcopolymer was separated and washed twice with 600 g of hexane, whereuponwhite solids were isolated. The white solids were vacuum dried at 50° C.for 24 hours, obtaining 50.6 g of the target polymer, Polymer 7′. Theresin was analyzed for composition by ¹H-NMR, finding that the copolymerconsisted of Monomers 1 and 6 in a ratio of 72/28 mol %. The copolymerwas also analyzed for molecular weight by GPC, finding Mw of 9,000 andMw/Mn of 1.4.

Next, in a nitrogen atmosphere, a 50 g portion of Polymer 7′ wasdissolved in 200 g of tetrahydrofuran. With the flask in an ice bath,4.6 g of triethylamine and 4.6 g of 1-chloro-1-methoxy-2-methylpropanewere added to the solution, which was continuously stirred for 10 hoursat room temperature. To the flask, 100 g of diisopropyl ether and 150 gof water were added, followed by stirring. After the water layer wasseparated off, the organic layer was concentrated. The concentrate wasadded dropwise to 750 g of hexane. The precipitated copolymer wasseparated and washed twice with 300 g of hexane, whereupon white solidswere isolated. The white solids were vacuum dried at 50° C. for 24hours, obtaining 44.1 g of the target polymer, Polymer 7. The resin wasanalyzed for percent protection of hydroxyl groups by ¹H-NMR, findingthat 28% of overall hydroxyl groups had been substituted by1-methoxy-2-methylpropyl groups. The copolymer was also analyzed formolecular weight by GPC, finding Mw of 9,200 and Mw/Mn of 1.4.

Comparative Polymer Synthesis Example 1

Synthesis of homopolymer of Monomer 9

To a flask in a nitrogen blanket, 100.0 g of Monomer 9, 3.91 g ofdimethyl 2,2′-azobis(isobutyrate), and 100.0 g of isopropyl alcohol werefed to form a monomer solution, which was kept at a temperature of20-25° C. To another flask in a nitrogen blanket, 50.0 g of isopropylalcohol was fed. With stirring, it was heated to 80° C., to which themonomer solution was added dropwise over 4 hours. After the completionof dropwise addition, the polymerization solution was continuouslystirred for 3 hours while keeping the temperature at 80° C. After thematuring, the solution was cooled to room temperature. Thepolymerization solution thus obtained was added dropwise to 2,000 g ofwater, after which the precipitated polymer was filtered. The polymerwas washed four times with 600 g of a 9/1 solvent mixture of hexane andisopropyl ether, whereupon white solids were isolated. The white solidswere vacuum dried at 50° C. for 20 hours, obtaining 92.8 g of the targetpolymer, Comparative Polymer 1. The polymer was analyzed by GPC, findingMw of 7,800 and Mw/Mn of 1.6.

Comparative Polymer Synthesis Example 2

Synthesis of homopolymer of Monomer 10

A homopolymer of Monomer 10 was synthesized in accordance with the sameformulation as in Comparative Polymer Synthesis Example 1. The polymer,Comparative Polymer 2, was analyzed by GPC, finding Mw of 7,900 andMw/Mn of 1.6.

Evaluation of Resist Coating

Resist solutions were prepared by dissolving 5 g of Resist Polymer(shown below), 0.5 g of an additive polymer selected from Polymers 1 to7 and Comparative Polymers 1 and 2, 0.25 g of PAG1, and 0.05 g ofQuencher 1 in 75 g of propylene glycol monoethyl ether acetate (PGMEA),and filtering through a polypropylene filter having a pore size of 0.2μm. A control resist solution was similarly prepared without adding theadditive polymer.

An antireflective coating ARC-29A (Nissan Chemical Co., Ltd.) of 87 nmthick was formed on a silicon substrate, after which each resistsolution was applied onto the ARC and baked at 120° C. for 60 seconds toform a resist film of 150 nm thick.

A contact angle with water of the resist film was measured, using aninclination contact angle meter Drop Master 500 by Kyowa InterfaceScience Co., Ltd. Specifically, the wafer covered with the resist filmwas kept horizontal, and 50 μL of pure water was dropped on the resistfilm to form a droplet. While the wafer was gradually inclined, theangle (sliding angle) at which the droplet started sliding down wasdetermined as well as receding contact angle. The results are shown inTable 2.

A smaller sliding angle indicates an easier flow of water on the resistfilm. A larger receding contact angle indicates that fewer liquiddroplets are left during high-speed scan exposure. It is demonstrated inTable 2 that the inclusion of the additive polymer of the invention in aresist solution achieves a drastic improvement in the receding contactangle of photoresist film without adversely affecting the sliding angle,as compared with the comparative photoresist films containingcomparative additive polymers and the control photoresist film.

Also, the resist film-bearing wafer (prepared above) was irradiatedthrough an open frame at an energy dose of 50 mJ/cm² using an ArFscanner S305B (Nikon Corp.). Then a true circle ring of Teflon® havingan inner diameter of 10 cm was placed on the resist film, 10 mL ofdeionized water was carefully injected inside the ring, and the resistfilm was kept in contact with water at room temperature for 60 seconds.Thereafter, the water was recovered, and a concentration of photoacidgenerator (PAG1) anion in the water was measured by an LC-MS analyzer(Agilent). The anion concentration measured indicates an amount ofanions leached out for 60 seconds. The results are shown in Table 2.

As is evident from Table 2, the photoresist films formed from the resistsolutions having the additive polymers of the invention compoundedtherein are effective for preventing the PAG component from beingleached out in water.

Further, the resist film-bearing wafer (prepared above) was exposed bymeans of an ArF scanner model S307E (Nikon Corp., NA 0.85, σ 0.93, 4/5annular illumination, 6% halftone phase shift mask), rinsed for 5minutes while splashing deionized water, post-exposure baked (PEB) at110° C. for 60 seconds, and developed with a 2.38 wt % TMAH aqueoussolution for 60 seconds, forming a 75-nm line-and-space pattern. Thewafer was sectioned, and the profile and sensitivity of the 75-nmline-and-space pattern were evaluated. The results are also shown inTable 2.

It is seen from Table 2 that when exposure is followed by water rinsing,the resist film having the additive polymer of the invention formulatedtherein formed a pattern of rectangular profile, in stark contrast withthe control resist film free of the additive polymer forming a patternof T-top profile.

TABLE 2 Receding Sliding contact Anion 75-nm Additive angle angleleach-out Sensitivity pattern polymer (°) (°) (ppb) (mJ/cm²) profilePolymer 1 10 81 7 34 rectangular Polymer 2 10 81 6 35 rectangularPolymer 3 11 78 7 33 rectangular Polymer 4 11 78 6 34 rectangularPolymer 5 10 82 6 35 rectangular Polymer 6 12 79 7 32 rectangularPolymer 7 5 90 7 32 rectangular Comparative 15 69 7 32 rectangularPolymer 1 Comparative 13 74 7 33 rectangular Polymer 2 not added 28 4060 45 T-top

Japanese Patent Application No. 2008-124476 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A resist composition comprising (A) a polymer P1 comprising repeatunits of the following general formulae (1a) and (2a), (B) a polymerhaving a structure containing one or both of a lactone ring and ahydroxyl group, and/or a structure derived from maleic anhydride, whichpolymer becomes soluble in an alkaline developer under the action of anacid, (C) a compound capable of generating an acid upon exposure tohigh-energy radiation, and (D) an organic solvent,

wherein R^(1a) and R^(1b) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl, R^(1a) and R^(1b) may bond together to form a non-aromaticring with the carbon atom to which they are attached, R² is hydrogen,methyl or trifluoromethyl, R³ is hydrogen or an acid labile group, a1and b1 are numbers satisfying 0<a1<1, 0<b1<1, and 0<a1+b1≦1.
 2. A resistcomposition comprising (A) a polymer P1′ comprising repeat units of thefollowing general formulae (1a), (1b) and (2a), (B) a polymer having astructure containing one or both of a lactone ring and a hydroxyl group,and/or a structure derived from maleic anhydride, which polymer becomessoluble in an alkaline developer under the action of an acid, (C) acompound capable of generating an acid upon exposure to high-energyradiation, and (D) an organic solvent,

wherein R^(1a) and R^(1b) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl, R^(1a) and R^(1b) may bond together to form a non-aromaticring with the carbon atom to which they are attached, R² is hydrogen,methyl or trifluoromethyl, R³ is hydrogen or an acid labile group,R^(4a) to R^(4c) are hydrogen or straight, branched or cyclic C₁-C₁₀alkyl, and a1, a2 and b1 are numbers satisfying 0<a1<1, 0<a2<1, 0<b1<1,and 0<a1+a2+b1≦1.
 3. A resist composition comprising (A) a polymer P1″comprising repeat units of the following general formulae (1a), (1b),(2a) and (2b), (B) a polymer having a structure containing one or bothof a lactone ring and a hydroxyl group, and/or a structure derived frommaleic anhydride, which polymer becomes soluble in an alkaline developerunder the action of an acid, (C) a compound capable of generating anacid upon exposure to high-energy radiation, and (D) an organic solvent,

wherein R^(1a) and R^(1b) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl, R^(1a) and R^(1b) may bond together to form a non-aromaticring with the carbon atom to which they are attached, R² is hydrogen,methyl or trifluoromethyl, R³ is hydrogen or an acid labile group,R^(4a) to R^(4c) are hydrogen or straight, branched or cyclic C₁-C₁₀alkyl, R⁵ is straight, branched or cyclic C₁-C₁₀ alkyl, and a1, a2, b1and b2 are numbers satisfying 0<a1<1, 0≦a2<1, 0≦b1<1, 0<b2<1, and0<a1+a2+b1+b2≦1.
 4. A resist composition comprising (A) a polymer P2corresponding to a polymer P1-H comprising repeat units of the followinggeneral formulae (1a) and (2a′) wherein some or all of hydroxyl groupsin formulae (1a) and (2a′) are protected with protective groups, (B) apolymer having a structure containing one or both of a lactone ring anda hydroxyl group, and/or a structure derived from maleic anhydride,which polymer becomes soluble in an alkaline developer under the actionof an acid, (C) a compound capable of generating an acid upon exposureto high-energy radiation, and (D) an organic solvent,

wherein R^(1a) and R^(1b) are hydrogen or straight, branched or cyclicC₁-C₁₀ alkyl, R^(1a) and R^(1b) may bond together to form a non-aromaticring with the carbon atom to which they are attached, R² is hydrogen,methyl or trifluoromethyl, and a1 and b1 are numbers satisfying 0<a1<1,0<b1<1, and 0<a1+b1≦1.
 5. The resist composition of claim 1, furthercomprising (E) a basic compound.
 6. The resist composition of claim 1,further comprising (F) a dissolution inhibitor.
 7. A pattern formingprocess comprising the steps of (1) applying the resist composition ofclaim 1 onto a substrate to form a resist coating, (2) heat treating theresist coating and exposing it to high-energy radiation through aphotomask, and (3) developing the exposed coating with a developer.
 8. Apattern forming process comprising the steps of (1) applying the resistcomposition of claim 1 onto a substrate to form a resist coating, (2)heat treating the resist coating and exposing it to high-energyradiation from a projection lens through a photomask while holding aliquid between the substrate and the projection lens, and (3) developingthe exposed coating with a developer.
 9. A pattern forming processcomprising the steps of (1) applying the resist composition of claim 1onto a substrate to form a resist coating, (2) forming a protectivecoating onto the resist coating, (3) heat treating and exposing thecoated substrate to high-energy radiation from a projection lens througha photomask while holding a liquid between the substrate and theprojection lens, and (4) developing with a developer.
 10. The process ofclaim 8 wherein the liquid is water.
 11. The process of claim 7 whereinthe high-energy radiation has a wavelength in the range of 180 to 250nm.
 12. A pattern forming process comprising the steps of (1) applyingthe resist composition of claim 1 onto a mask blank to form a resistcoating, (2) heat treating and exposing the resist coating in vacuum toelectron beam, and (3) developing with a developer.